<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <button>按钮1</button>
    <button>按钮2</button>
    <button>按钮3</button>
    <button>按钮4</button>
    <button>按钮5</button>

    <script>
 
       var btn = document.getElementsByTagName('button');

       for(var i=0;i < btn.length;i++){
       btn[i].onclick = function() {
          for(var i=0;i<btn.length;i++){
             btn[i].style.backgroundColor = '';
          }
          this.style.backgroundColor = 'pink';
       }
    }


    </script>
    
</body>
</html>